Manufacture of zinc oxid



W. L. COURSEN.

-' MANUFACTURE OF ZlNC-OXID. APPLICATON FILE!) JUNE28. 1920.

1 ,372,486 Patented Mar. 22, 1921.

%13 &tte 040 13 UNITED ,STATES PATENT OFFICE.,

WALTERZLESLIE COURSEN, or PALMERTON, PENNSYL ANIA, ASSIGNOR 'ro THE m'a-.w

JERSEY zmc COMPANY, or NEW YORK, N. Y., A CORPORATION OENEW JERSEY.

MANUFAC''URE or ZINC oxn.

Specificationof Letter's ratent. Pate'ted luar. 22, 1921.

Application filed June 28, 1920. Serial No. :392,204.

To all whom ?It may concern:

Be it known that I, WALTER LESLIE COURSN, a citizen of the United States, residing .at Palmerton, in the county of Carbon, State ofvPennsylvania, have invented certain new and useful Improvements in the Manufacture of Zinc Oxid; and'I do hereby declare the following to be a full, clear, and

exact description of the invention, such as I will enable others skilled in the art to which it appertains to make and use the same;

This invention relates to the production of French oxid (i. e., zinc oxid) by the retort volatilizing process.

In the production of French oxid by the retort volatilizing process, it is the common pacity during only a part of the time. This intermitten method of operation requires frequent cleaning of the retorts, while the retorts themselves not^infrequently crack or fail and must be replaced, thus' further decreasing the output of the furnace and increasing the labor and expense of operation. So also, such intermittent operation of the retorts is wasteful of fuel'for the reason that the retorts must be'heated during the time interval between the end of one operation and the beginning of' the next, as well as during the preliminary period of melting the zinc and heating it to the required tempera other advantages, which will more fully ap pear from the following description.

In the application of James A. Singmaster, Serial No. 370,082, filed March 31, 1920, there is described an improved method of producing French oxid by the retort volatilizing process according to which the operation is carried out in a substantially continuous manner. The process of the present invention involves a similar continuous operation, but involves an improvement upon or modification of the process of said prior application. According to the process described in said prior application, the volatilizing retort is charged with moltenzinc,

and further amounts of molten zinc are,

charged from time totimeto make up for that which has' been volatilized. According to the present invention the retort iS charged with solid zinc, instead of with molten zinc, but the operation is carried out with the maintenance of a substantial body of molten zine' in the retort, to which the increments of solid zine are added from time to time, so that a similar continuous operation is obtained to that which is obtained when the retort is kept supplied with further amounts of molten zine. V

'In the practice of the present invention, a. preliminary charge of zinc or spelteris charged into the retort and the retort is brought to the temperature required for the Volatilizing operation. amounts of solid zinc areadded to the retort from time to time to make up for that which Thereafter, further.

is volatilized, but such further additions of 4 zine are relatively small in amount *and a substantial body of molten zine is retained in'the retort, so that the retort operation is continuous, and the oxid production is .likewise' of a substantially continuous character, except for the eriod of time' required for melting the added zinc and again bringing the contents of the retort to the volatilizing temperature. p,

In the practice of' the invention, it is advantageous to maintain a suflicient body of molten zine in the retort so that the retort will operate at approximately its maximum working Capacity and so that the additions of solid Zinc from time to time will not result in undue cooling of the contents of the retort. With such a body of molten Zinc in the retort, the zine whch is added will be rapidly melted and brought to the volatilizing tem- I in the retort.

perature, so thatsmall increments of solid zine can be added from time to time without seriously interfering with the continuity of the operation. The maintenance of a substantial body of mo'lten zine has the further advantage of equalizing any inequalities in any objectionable amount of volatilization by' maintaininga substantial body of zine in the retort, whereas, if the charge were entirely worked oli, asin common practice, volatilization of lead would take place. Accordingly, by maintaining a suflicient excess of zine in the retort, inequalities in lead-contained in the zine charged will be neutralized and the lead can be made to accumulate When the lead has thus accumulated to such an eXt'ent as to inte'rfere with the desired uniformity and purity of the product, the lead-containing residue can then be withdrawn from the retort. Accordingly, by maintaining a suflieient excess of molten zine in the retort, a product of' hi h purity y and great uniformity can be obtaned even where the molten zine charged contains varyin amounts of lead.

n the preferred practice of the invention, the zine is supplied in the form of sticks o' bars of relatively small size, such that they can. be readily charged into the retorts. These sticks or bars can be readily provided by casting molten zine or spelter in specially designed molds, instead of casting in the form of slabsaccording to the present practice. By providing the zine or spelter in the form' of relatively small and uniform' sticks, the operator is 'able to supply to the individual volatilizing retorts one or more sticks from time to time to make up for the zine' which has volatilized. These sticks, being of small size, are rapidly melted by the highly superheated body of molten zine within the retorts.

The'invention will-be further illustrated by the following more detailed description,

of the retorts showing the level of the eharge the ein 5 Fig. 5 is a plan of a suitable formof mold; and i 'Fig. 6 is an enlarged cross-section of a suitable form of stick or bar of zine or spelter.

Referring to the drawing, the furnace 1 may be of any suitable Construction, for example, it may be a regenerative gas-fired furnace, and it has therein a series of volatilizing retorts 2, twenty in number in the furnace illustrated. In the operation of a regenerative gas-fired furnace, the supply of air and gas is reversed from time to time so that combustion takes place first from one end of the furnace and then from the other,

the waste products of conbustion serving to heat the regenerators alternately in the usual 'l he retorts 2 may-be of an suitable construction. As illustrated in igs. 2, 3 and 4, they have the usual dam 3 at one end and the usual opening 4 thereabove and are closed at the other end by a closure or luting 5 through which extends the pipe 6 for supplyin the reducing gas. This pipe 6 has a door through which the sticks of zine can be introduced.

The sticks of zine for charging the retorts can be made by casting molten zine or spelter in special molds. One suitable form of mold is indicated in Fig. 5, this mold having a series of depressions 8 for casting a series of sticks or pigs. The molten zinc or spelter can be poured into the depression 9 and permitted to flow into the individual lateral depressions, ina manner similar to that used in' casting pig iron. The individual sticks or pigs can then be broken ofl' from the sow and used for chargi'ng the retorts. The

sticks thus cast can vary somewhat in size and length. -A suitable size is about 18 to 24 inches long and 1 to 2 inchesflin width and source: The casting of the zine, to form the sticks, by the use of a suitable finger mold of the character above described, will be readily understood without furtherdeseription, being similar to the common methods of casting spelter in slabs except for the form of mold employed.

In the production of the French oxid, the retorts are externally heated to a temperature above the volatilization point of zine but below the volatilization point of lead, iron, etc., and,the retorts are kept filled with a reducing gas, such as clean producer gas introdueed through the pipe 13. The introduction of this gas prevents premature oxidation of the zine vapor and also assists in sweeping out the zine vapor as fast as it is formed, thereby promoting its formation. The zine-vapor and the producer gas combine withthe oxygen of the air at the -These sticks will. be first melted to form a of zine should be made from time to time to maintain the level at approximately the maximum working Capacity of the retort. linasmuch as the molten zine is at a temperature considerably above the melting point of the added zinc, this Zinc will be rapidly melted and the charge will soon again reach the necessary temperature for y volatilization. For example, in the volatilizing retort which holds a charge of about 225 pounds of molten Zinc, the individual sticks may have a weight of around 6 to 8- pounds, and it Will be evident that such stieks will be soon melted after they are added to the molten zine in the retort.

By maintaining a substantial body of molten Zinc in the retort, there is a maximum surface exposure for volatilization, and approximately the maximum contact surface between the molten ZIC and the walls of the retort through which the heat is transferred. Effective heating of the molten zinc in the retort and effective volatilization thereof are thus Secured.

The retort is preferably filled to about the level indicated in Fig. 4, and further additions are made from time to time to prevent the level from falling too low, so that the retort will be operated at approximately its maximum working Capacity.

When it becomes necessary to clean a retort and remove the ashes or the residual moltem metal therefrom, the closure 5 can be broken away to permit this cleaning op eration. The retort can then be again charged with sticks of Zinc andthe retort (closed by luting with clay or other material which will bake and form a solid closure by the time the solid Zinc has melted.

By Operating in the manner above described, it has been found that the producing` Capacity of the retorts can be very greatly 'inc-eased. It has thus been found that a regular furnace which will consume about 150 tons of metal per month, with the zine charged cold into the retorts, and the reto'ts operated ii :n intermittent manner i will consume as high as 210 tous or higher scontinuity of operation with a substantial that volatilized.

per month, when the furnace is operated in a substantially continuous manner, according to the present invention, even though the Zinc is charged cold into the retorts.

This greatly inereased Capacity and yield is due, as I believe, to the approximately constant and maximum heat transfer through the retort walls, owing to the large contact area between the Inolten zine and the heated walls of the' retort, and to the continuity of the operation with a substantial body of molten zine in the retorts, to

.which the stcks of solid zine are added.,

and by which they are rapidly nelted The body of zine in the retorts, avoids the time lost in intermittent operations for complet- `ing the` working oli of the individual charges, cleaning the retorts, recharging the retorts intermittently, and melting and .bringing each successive charge to the volatilizing temperature.

The improved process of the present invention' presente many of' the same or similar advantages to those presented by the process of said Singmaster application, Serial No. 370982, to wit, the advantage of increased Capacity and yield, together with high zine recovery and low -operating cost, prolongation of the life of the retorts with resulting reduct-ion in'zinc losses, less frequent renewal of the retorts, increased economy and efficieney of fuel, reduotion in the labor required-in cleaning and replajcing the' retorts, less frequent cleaning of thereto rts, etc. 'The present invention presents the further advantage that the zinc charged into the furnace s in a form readily handled and readily regulated in amount. The operator can thus go from one'retort to another, and charge one or more of the solid sticks of zine into the retort. The present invention thus makes possible the charging of solid zine into theretorts in a simple and advantageous manner, *while nevertheless obtaining the. advantages of continuity of operation, increased fuel economy, etc.

I claim:

1. In the production ef French oxid `by the retort volatilizing process, the improve- 115 ment which comprises maintaining a substantial body of molten zine in the retort and adding further amounts of solid zine thereto from time to time to make up for that which has been volatilized.

2. In the roduction of French oxid by the retort vo atilizng process, the improvement whichcomprises Operating the retort in a substantially continuous manner and at approximately the maximum working capacity of the retort by maintaining a substantial body of molten zine in the retort and adding further amounts of solid Zinc thei-eto from time to time to make up for llO 3. In the production of French oxd by the retort volatilizing process, the improvement which comprses maintaning a substantial body of molten Zinc in the retorts and adding thereto from time to time further amounts of Zinc in the form of relatively small sticks or bars which are readily melted by the molten Zinc in the retorts.

4. In the production of French oxid by' the retort volatilzing process, theimprovement which comprises maintaining in the volatlizing retort a substantial body of molten Zinc having a large contact surface with the walls of the retort, and supplying to the retort from time t'o time further amounts of zinc in the form of relatively long and small sticks or rods, whereby effective heat transfer takes place through the Walls of the retort to the molten Zinc therein and the added Zinc is rapidly n'eltcd thereby.

5. In the production of French oxid by the retort volatilzing process, the improvement which comprises maintaining a substantial body of zinc in the yolatilizing retorts, adding thereto from time to time further amounts of lead-containing Zinc in solid form, maintaining a suflicient excess of zinc in the retorts to hold back lead from volatilizing and thereby pernitting lead to accumulate in the retort, and finally withdrawing the residue rich in lead from the retort. 4

In testimony whereof I afiix my signature.

WALTER LESLIE COURSEN. 

